1. Field of the Disclosure
The present invention relates generally to power converters, and more specifically, the invention relates to sensing input and output voltages of power converters.
2. Background
Many electrical devices such as cell phones, personal digital assistants (PDA's), laptops, etc. are powered by a source of relatively low-voltage DC power. Because power is generally delivered through a wall outlet as high-voltage AC power, a device, typically referred to as a power converter is required to transform the high-voltage AC power to low-voltage DC power. The low-voltage DC power may be provided by the power converter directly to the device or it may be used to charge a rechargeable battery that, in turn, provides energy to the device, but which requires charging once stored energy is drained. Typically, the battery is charged with a battery charger that includes a power converter that meets constant current and constant voltage requirements required by the battery. In operation, a power converter may use a controller to regulate output power delivered to an electrical device, such as a battery, that may be generally referred to as a load. More specifically, the controller may be coupled to a sensor that provides feedback information of the output of the power converter in order to regulate power delivered to the load. The controller regulates power to the load by controlling a power switch to turn on and off in response to the feedback information from the sensor to transfer energy pulses to the output from a source of input power such as a power line.
Power converter control circuits may be used for a multitude of purposes and applications. There is a demand for control circuit functionality that can provide all features demanded for the application while reducing the number of components outside the integrated control circuit. This reduction in external component count enables miniaturization of the power converter to improve portability, reduces the number of design cycles required to finalize a power converter design and also improves reliability of the end product. Furthermore, reduced component count can offer energy efficiency improvements in the operation of the power converter and can reduce the power converter cost. Some example additional features that improve on regulation and detect additional fault conditions in the power converter rely on sensing an input line voltage. In some cases, sensing an input line voltage may be necessary in order to meet customer requirements. However, known circuits that sense an input line voltage add components external to the controller. An integrated solution would eliminate discrete components needed to sense the input line voltage, but in some cases integrating a circuit that senses an input line voltage may result in the need for additional terminals, which may increase the size, cost and complexity of the integrated controller.